DE4323573C2 - Method for determining a cutting trajectory in an NC machining system - Google Patents

Description

The invention relates to a method for determining cut trajectories for a Ball head machining device with a small diameter in one NC (numerical control) machining system for cutting one Remaining area on a workpiece, which is created by machining the Workpiece with a large diameter ball head machining device, wherein the remainder area is an area that is formed from remainder cut that when cutting along the respective cutting trajectories of the sphere Head processing device with a large diameter remain unprocessed.

Such a method is published in Japanese Unexamined Patent Lichung No. 3 (1991) -62204 known. The processing takes place for example on the Basis of three-dimensional shape data, which is supported by CAD (computer-aided de sign) are provided. In the known method, a computer is used to control the NC machining system.

When doing a mold with a complicated curved surface tet, the surface of a workpiece is cut or removed directly men using NC data from CAD (computer-aided design) data are prepared without using a plaster cover mold or the like. In the NC machining system, the tool is used to cut the workpiece kes is initially positioned away from the workpiece and is then towards the workpiece is moved in order to work with the workpiece on a part to be cut or Section to be brought into contact. After cutting the section the tool is removed from the workpiece and becomes another intersecting section moves, if there is one, and is finally in the original position returned. The path or path along which the Tool moves on every part to be cut during the cutting operation  is determined based on the shape of the surface to be formed thereon che, using the CAD data.

In the present description of the invention, the path of the tool, along which the tool to be cut at each during the cutting operation Section is moved, referred to as "section trajectory". The path or the train of the tool along which the tool is cut during the entire cutting operation is moving, including the path along which the tool in Rich the workpiece from the original position to the tool inlet de or start of the cutting trajectory for the first section to be cut the path along which the tool is moved from the tool outlet end the cutting trajectory is returned for the last section to be cut, the paths along which the tool is moved from section to section, and also the respective cutting trajectories, is used in this invention as a "tool career "or" tool path course "to make a distinction here to create.

When a workpiece is cut or milled with a milling cutter or a machining device with a ball head, an area at a corner section of the workpiece remains uncut or unprocessed, as can be seen from FIG. 11, when the diameter R of the ball head of the milling cutter is great. (The unprocessed section is referred to in the present description as "remaining section").

The rest of the section has to be edited or finished later, which a deterioration in accuracy and an increase in man hours leads. If, on the other hand, the workpiece with a milling cutter with a ball head such a small diameter that the corner section bear without a remaining section can be cut, the tool feed speed must be in greatly reduced, resulting in a sharp increase in machining lead time.  

In view of these problems, the remaining section, which is cut by a milling cutter with Ku large diameter gel head is produced using a variety of tools are cut or machined one after the other, their diameters gradually decreases. In order to carry out this procedure, the cutting trajectories for the Milling with the small diameter ball head in addition to those for the Milling machine can be prepared with the large diameter ball head.

When a workpiece is cut with a plurality of ball end mills with different diameters, the cutting trajectory is conventionally also prepared for the small diameter (r) ball end mill over the entire cutting surface of the workpiece, as shown in FIG. 12. Then, the remaining portion is determined while reading the drawing, and is shown by broken lines approximating the shape of the curved surface to be molded, as shown in Fig. 13A. Then, the part of the cutting trajectory other than the part for the remaining portion is trimmed, and the cutting trajectory for cutting the remaining portion with the small-diameter ball end mill in the same direction as the direction of the cutting trajectory for the large-diameter ball end mill is obtained from the computer issued.

According to the conventional method described above, it is a very long time required to calculate the cutting trajectory data by the computer, and due to the large amount of data, a large capacity memory is required such.

Furthermore, the determination of the remaining section requires the representation of the Re section through the dashed lines and the cutting of the cutting trajectory, what is carried out by the operator, a long time, and at the same time ver the accuracy of the data deteriorates due to such manually executed Editing operations.  

Furthermore, since the remaining section is formed as an elongated area, the perpendicular to the cutting trajectory for the large diameter ball end mill extends, the small diameter ball end mill must pass many times over a very short distance can be moved back and forth, which increases the processing time elevated.

Given the observations and description above, it is the task be the present invention, a method for determining to specify the section trajectory, which includes both the man hours and the machining time can be greatly reduced if using a ball end mill large diameter generated residual section with a ball end mill with a small Diameter is cut or machined.

This object is achieved in the method of the present invention by Steps: Identify the remaining sections along the lines that are regularly spaced apart spaced cutting trajectories for the ball head machining device with large Diameter, obtaining reference cut trajectories for ball head machining processing device with a small diameter, which would then be the cutting trajectories If the workpiece is only machined on the remaining sections with the ball head device with a small diameter in the direction of the cutting trajectories for the Ball head machining device with large diameter cut or bear would be subdivided into all reference cut trajectories with the same number from division points on these into regular intervals or sections along the respective reference cutting trajectory, determining the cutting trajectories for the ball head machining device with small diameter by connecting of the respective division points on the respective reference intersection trajectories straight lines.

In a preferred embodiment of the present invention, the Re reference intersection trajectories when the lines that are connected by connecting the corresponding  End points of the reference cut trajectories are obtained, are sharper curved corrected as a predetermined degree such that the Lines are smoothed, with all reference cut trajectories (S1 to S8) after the Correction can be divided.

Furthermore, it is preferable if the number of division points is based on the longest reference cut trajectory is determined.

Further advantages, features and possible uses of the present invention tion result from the following description of exemplary embodiments in connection with the drawing.

Fig. 1 is a schematic view showing a manner of identifying the remaining portion and preparing the reference cut trajectory;

Fig. 2 is a schematic view showing the reference cut trajectories in the remaining area;

Fig. 3 is a perspective view showing an example of the surface to be cut;

Fig. 4 is a plan view of the same;

Fig. 5 is a sectional view taken along the line AA in Fig. 4;

Fig. 6 is a sectional view taken along the line BB in Fig. 4;

Fig. 7 is an enlarged sectional view showing a part of Fig. 5 superimposed on the corresponding part of Fig. 6;

8A and 8B are each a view showing the method of correcting the Schnitttrajektorien data for the ball end mill of small diameter.

Fig. 9 is a view showing the manner of determining the cutting trajectories for the small-diameter ball end mill;

Fig. 10 is a flowchart showing an example of the operation of the computer when the cutting trajectories are determined for a plurality of ball end mills using the method of the present invention;

Fig. 11 is a schematic view showing the section produced by a large diameter ball end mill;

Fig. 12 is a schematic view showing the sectional trajectory of the small-diameter ball end mill when cutting the remaining portion according to a conventional method; and

FIG. 13A and 13B are views for illustrating the forth conventional method for determining the Schnitttrajektorien for the ball head milling with small diameter.

According to an embodiment of the present invention, the remainder portion generated by a large-diameter spherical head machining device (hereinafter referred to as milling cutter) is identified in the following manner. That is, in Fig. 1 is a circle with a diameter equal to the diameter R (z. B. 25 mm) of the large diameter ball end mill and with a center O on the path of movement of the center of the spherical tip of the large diameter ball end mill in the Shown plane showing the cutting trajectory for the large diameter ball end mill, extending along the cutting surface W of the workpiece, and is perpendicular to the cutting surface W, and when the circle touches the cutting surface W at two points P1 and P2 the area between two vectors (nor paint) N1 and N2, each connecting the center O and the contact points P1 and P2, as the rest of the section D determines or determines.

The cutting trajectory S for the ball end mill with small Diameter with a diameter of r (e.g. 10 mm), when the small diameter ball end mill does the rest section D in the direction of the cutting trajectory Q for the Ball end mill with large diameter cuts between the points Ps and Pe. The points are Pe and Ps Points where the path of movement is the center of the spherical tip of the ball end mill with a small diameter along the intersection trajectory S, the vectors N1 and N2 cuts. The intersection trajectory S forms the reference cutting trajectory.

Such a reference slice trajectory S is obtained for each of the cutting trajectories for the ball end mill large diameter, and the cutting trajectories for the Ball end mill with small diameter are within the Area created by the three-dimensional curve around is written or surrounded by the endpoints of the Reference intersection trajectories S runs.

Fig. 2 shows the simplified residual portions M. In FIG. 2, S1 to S8, the Referenzschnitttrajektorien S.

Fig. 3 is a perspective view showing the surface to be cut of a die. The reference cut trajectories S are shown at fine intervals on the surface W to be cut or machined by lines which are written or written at regular intervals or intervals in the directions of the X-axis and Y-axis on the top view or on the top view 4, which is shown in FIG .

FIGS. 5 and 6 are sectional views taken along lines AA and BB in Fig. 4. In Fig. 5 referred to QA, the cutting trajectory for the ball end mill with large diameter in cross-section along the line AA, SA denotes the Referenzschnitttrajektorie in the cross section along the line AA, and WA denotes the area to be cut in the cross section along the line AA. Similarly, in Fig. 6, QB shows the cutting trajectory for the large diameter ball end mill in the cross section along the line BB, SB denotes the reference cutting trajectory in the cross section along the line BB, and WB denotes the surface to be cut in the cross section along the line Line BB. Fig. 7 is an enlarged cross-sectional view and shows a part of Fig. 5 superimposed with the corresponding part of Fig. 6th

As can be seen from FIG. 7, the reference cutting trajectories SA and SB differ from one another in the length and in the position of the end points. That is, Fig. 2 shows schematically that the lengths of the remaining sections, as measured in the direction of the cutting trajectories for the large diameter ball end mill, differ from one another in a rest area or a residual area M ( FIG. 9), the remaining sections in the direction the X axis are continuous.

After the remaining sections generated by the large-diameter ball end mill are identified and the reference cutting trajectories S1 to S8 for the respective remaining sections are obtained in the manner described above, the corresponding end points of the reference cutting trajectories S1 to S8 are each connected by straight lines, as indicated by the Dashed lines in Fig. 2, and the degree or degree of bending of the respective paths L1 and L2, which are formed by the straight lines between adjacent reference intersection trajectories, is determined. If the degree of bending of paths L1 or L2 is greater than a predetermined value, path L1 or L2 is corrected to become smoother.

That is, if the angle between two straight lines that intersect at end points, e.g. B. when the angle 61 ( FIG. 8A) between the straight line connecting the end points of the reference intersection trajectories S5 and S4 and the straight line connecting the end points of the reference intersection trajectories S3 and S4 is larger than a predetermined angle θ , the reference cut trajectory S4 is shortened so that the angle θ1 becomes equal to the predetermined angle θ.

In another method of correction, when the distance d1 ( FIG. 8B) between the end points of a reference intersection trajectory, e.g. B. S4, and the line connecting the end points of the reference cutting trajectories S3 and S5 adjacent to the reference cutting trajectory S4 on opposite sides thereof, is greater than a predetermined distance d, the reference cutting trajectory S4 is shortened so that the distance d1 is equal to that predetermined distance d.

Then, the longest reference cut trajectory (S4 in this example) is selected and divided as shown in Fig. 9 at a plurality of points (four in Fig. 9) at regular intervals equal to the cut distances or pitches of the Ball end mill with a small diameter in the direction of the reference cutting trajectory. Then, the other reference intersection trajectories S1 to S3 and S5 to S8 are divided with the same number of points, and the lines V1 to V6, which are obtained by connecting or plotting the respective division points on the respective reference intersection trajectories S1 to S8, are used as the intersection trajectories for determines the ball end mill with a small diameter.

That is, the cutting trajectories that are according to the present Invention to be obtained extend in the longitudinal direction the remaining area or the remaining area M. Accordingly, the Processing time can be shortened compared to the case in which the remaining area M along the reference section trajectory toria S1 to S8 is cut, and the load on the Small diameter ball end mill is reduced and made uniform.

Since the remaining sections continue to be identified automatically and the cutting trajectories only for the rest sections can be created for editing the Cutting trajectories require man hours be reduced.

Fig. 10 is a flowchart showing an example of the operation of the computer when Schnitttrajektorien of the present invention be determined for a plurality of ball head milling using of the proceedings.

In Fig. 10, the computer first reads the CAD data (step S1). Then, the computer calculates the cutting trajectories for the largest diameter ball end mill based on the CAD data (step S2). Then, the computer identifies the remaining area generated by the ball end mill with the largest diameter in the manner described above and calculates the reference cut trajectories for the ball end mill with the second largest diameter (steps S3 and S4). Thereafter, the computer corrects the reference cut trajectories in the manner shown in Figs. 8A or 8B, if necessary, and calculates the cut trajectories for the ball end mill with the second largest diameter (steps S5 and S6). The computer then determines whether any sections or parts remain uncut or unprocessed in step S7. If it is determined that a part remains unprocessed, the computer selects the ball end mill with the third largest diameter (step S8) and repeats steps S3 to S8 until the unprocessed part or section remains. Then, the computer stores the cut trajectories thus determined in a memory or outputs them (step S9).

Claims (4)

1. A method for determining cutting trajectories for a ball head machining device with a small diameter ( 2 r) in an NC machining system, namely for cutting a residual area (M) on a workpiece, which is generated by machining the workpiece with a ball head machining device with a large diameter ( 2 R), the remaining area (M) being an area or an area which is formed from residual sections (D) which, when cutting along the respective cutting trajectories (Q), of the large-diameter spherical head machining device ( 2 R) remain unprocessed, the process comprising the steps of:

• Identifying the remaining sections (D) along the regularly spaced cutting trajectories (Q) for the large diameter ball head machining device ( 2 R),
• - Obtaining reference cutting trajectories (S) for the small-diameter ball head processing device ( 2 r), which would be the cutting trajectories if the workpiece was only at the remaining sections (D) with the small-diameter ball head processing device ( 2 r) in the direction of the cutting trajectories (Q ) would be cut or machined for the large diameter ( 2 R) ball head machining device,
• - Subdivide all reference intersection trajectories (S) with the same number of division points lying on them into regular intervals or sections along the respective reference intersection trajectory (S),
• - Determining the cutting trajectories (V1 to V6) for the ball head processing device with a small diameter ( 2 r) by connecting the respective division points on the respective reference cutting trajectories (S1 to S8) by straight lines.

2. The method according to claim 1, wherein the reference cut trajectories (S1 to S8) then when the lines are made by connecting the appropriate endpoints of the reference cut trajectories (S1 to S8) are obtained, more sharply curved are such as a predetermined degree or dimension (θ; d) corrected that the lines are smoothed, and all Reference slice trajectories (S1 to S8) can be divided after the correction. 3. The method according to claim 1 or 2, wherein the number of division points on the Basis of the longest reference cut trajectory (S4) is determined. 4. The method according to claim 1, wherein the remaining portion (D) is determined so that a circle with a diameter larger than the diameter of the ball head machining device ( 2 R) has the same diameter and with a center (O) lying on the cutting trajectory (Q) in such a way is placed in the plane of the intersection trajectory that the circle touches the machined surface at two points (P1, P2), and the remaining section (D) is between two vectors (N1, N2) connecting the two points to the center (O) , where the cutting trajectory (Q) corresponds to the path of movement of the center of curvature of the tip of the ball head machining device.